Bae Youngmi is a young detective with a long enemy list. When she’s faced with the biggest case of her life, nothing should distract her. Everything’s on the line, her sister, her mother, the honour of her deceased father, her friends and a four year old son who could possibly pose as the killer’s hostage. But what happens when the case makes an unusual turn after one suspicious guy by the name of Lee Joon walks into her life claiming that he’s a detective that was sent to Seoul from the Busan unit with a case that’s similar to the one they’re dealing with now. Now one of her best friends is the victim of the psycho that they’re hunting. The bureau has no choice but to listen to the story of the mystery man, but what happens when he says he knows Youngmi who has no idea who this guy is? He says that the killer is after her.

On the side of having to juggle being a full-time working single mom, Youngmi has to deal with the tempting forbidden office romance that attractive co-worker AJ aka Lee Gikwang is offering. Something would have developed by now, but ever since the case and the entry of the mystery man things seemed to have stalled.

Things take the turn for the worst when the killer’s MO changes for the worst for Youngmi. Now it’s life or death for the young mother and her son. This psycho has something he wants and he just can’t seem to get that something. Can Youngmi give up and trust Joon before it’s too late or is he just too suspicious to trust? Will Gikwang and Joon get along for the sake of Youngmi, or will they let their differences get the best of them and let this killer slip away?